Merodon natans group (Diptera, Syrphidae) taxa are reviewed using an integrative taxonomic approach combining morphological, morphometric and molecular techniques. The approach substantiates recognition of the three species: M. calcaratus (Fabricius, 1794), M. natans (Fabricius, 1794) and M. pulveris Vujić & Radenković in Radenković et al. 2011, and reveals the existence of a new species, M. makrisi Vujić, Radenković & Tot sp. nov., which is described. It also highlights the existence of a series of natans group populations, especially on some of the Mediterranean islands, in the Levant and in the Afrotropical Region, for which more comprehensive data are required to clarify their status. A key is provided to the natans lineage species currently recognised, and preimaginal stages of some natans-group species are described for the first time. Redescriptions for M. calcaratus and M. natans are provided. A neotype is selected for M. natans. Lectotypes are designated for M. annulatus (Fabricius, 1794) and M. melancholicus (Fabricius, 1794). Merodon annulatus is recognised as a synonym of M. natans.
Overwinter survival of hibernators is directly influenced by the fat reserves accumulated during the active season. The European ground squirrel, Spermophilus citellus, an endangered flagship species of the open grasslands of central and southeastern Europe, is no exception. Considering anthropogenic changes affecting its habitats in northern Serbia, we studied the species? feeding habits by subjecting its feces to microhistological examination. In addition to identifying plant remains in the feces, we examined the vegetation of the four study sites located inside a local mosaic of steppe and saline pastures. Our findings indicate that these remaining European ground-squirrel sites are diverse and stable grasslands covered by native flora that represents a complete dietary base for the species. The diet is dominated by a small number of plant species, specifically Achillea millefolium, legumes and grasses, with sporadic contributions from a number of other species. The diet of S. citellus also differs by location and season in that grasses dominate during the early season, while A. millefolium takes precedence later in the year. This dietary information is essential for the development of future species and habitat management strategies. In light of the predicted impact of climate change on grasslands in northern Serbia, our findings will be instrumental for translocations and conservation actions in the future.
Understanding the spatial and temporal effects of variable environmental conditions on demographic characteristics is important in order to stop the decline of endangered-species populations. To capture interactions between a species and its environment, in this work the demographic traits of the European ground squirrel (EGS), Spermophilus citellus, were modeled as a function of agricultural landscape structure. The habitat suitability index was determined for 20 localities within the study area based on habitat use, management and type. After mapping the habitat patch occupancy in the field, crop cover maps, the average normalized difference vegetation index (NDVI) and automated water extraction index (AWEI) were obtained from satellite images covering the period 2013-2015. This data was used to develop population-level generalized linear models (GLMs) and individual-level conditional mixed-effects models (GLMMs) in R package Ime4, focusing on the key demographic traits of the EGS. The land composition and patch carrying capacity (PCC) are the key determinants of the endangered EGS population size, while system productivity is the main factor influencing individuals' body condition after monitoring for variations across sampling years and age classes. The proposed landscape structural models show that human activities and abiotic factors shape the demographic rates of the EGS. Thus, to conserve threatened species, an appropriate focus on the spatial adaptation strategies should be employed.
The European roller (Coracias garrulus) is an endangered species whose breeding in Serbia depends almost entirely on nest boxes. The aim of the present study was to assess the influence of prey availability and foraging habitat characteristics on nest-box occupancy and breeding parameters. Data from 20 roller foraging sites over 5 breeding seasons were used in a set of linear regression models to evaluate which factors affect the diversity and biomass of roller prey, as well as nest-box occupancy and breeding parameters. Our analyses revealed that prey availability parameters were significantly affected by the grazing regime and biophysical parameters. An area under grassland negatively affected nest-box occupancy, clutch size and fledging success. In contrast, grazing intensity showed positive effects. Although grazing negatively affected prey diversity and quantity, it potentially increased the likelihood of a successful hunt by forming short vegetation. These results indicate that the habitat characteristics linked to the ability of the species to hunt successfully should be considered when installing nest boxes as a part of the broader management of roller breeding sites. Furthermore, nest-box installation in open agricultural habitats other than grasslands should be considered in the conservation strategy for the species in Serbia.
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